Did you lose the entire document package from closing or just the title policy?
Either way, start by contacting the company who performed your closing and issued the title insurance. If you are lucky they will still be in business and have an easily accessible data base. If you contacted my office, I could e-mail you a pdf of your entire file while we were chatting on the phone. Most companies aren't that accessible though, so let's assume you aren't having any luck there.
If you have a copy of the HUD-1 Settlement Statement, look at the 1100 section and see if you paid for title insurance. A premium paid on a HUD-1 is evidence of title insurance. The HUD-1 may even have the name of the actual title insurance company. Google them or contact your state insurance department for assistance. Contact the company and ask for a copy of your policy. It may take time but they should be able to track it down. By time, I mean it could take months, because title companies don't always have a good way of tracking title policies.
If you can't find the HUD-1, your mortgage lender, Realtor or even the seller may have a copy that they will share with you. Good luck and let this be a reminder to all to keep those documents in a safe place. ;)